The present invention relates to medical diagnostic ultrasonic imaging systems and methods, and in particular to such systems and methods that utilize coded transmit pulses to enhance imaging characteristics. Certain embodiments of this invention are particularly useful in motion processing imaging modes such as 2D or 3D color flow imaging, spectral Doppler imaging, tissue motion imaging, strain imaging, and pulse inversion harmonic Doppler imaging. Harmonic imaging embodiments can be used in contrast agent imaging modes as well as in tissue harmonic imaging modes. Other embodiments are particularly useful for B-mode processing.
Frequency modulated (FM) transmit pulses are known in the art for increasing average power of a signal without increasing the instantaneous peak power. This technique has been recently suggested in the medical ultrasound field for use with B-mode imaging (M. O'Donnell, Coded Excitation System for Improving the Penetration of Real-Time Phased Array Imaging Systems, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 39, No. 3, pg. 341-351, May 1992), as well as in conjunction with contrast imaging (Y. Takeuchi, Coded Excitation for Harmonic Imaging, Ultrasonics, PH-3, 1996).